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Did you just recently have the update? Also how did you run your test? Can you walk me through your calculations?
No update on a 2020.
I went from 100% DIC (97.36% Raw) and drove it down to around 40% SoC one day and then the next day got it down to 2.353% DIC (3.445% Raw) and the display said I had used 62.2 kWh.
So I calculate 63.70 kWh (62.2/(1-.02353)) usable. I drove around the charger a little and got the used up to 62.4 with no change in DIC so that would be 63.90 kWh.
Torque said capacity est. 59.18 kWh.
 

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Discussion Starter · #1,283 ·
No update on a 2020.
I went from 100% DIC (97.36% Raw) and drove it down to around 40% SoC one day and then the next day got it down to 2.353% DIC (3.445% Raw) and the display said I had used 62.2 kWh.
So I calculate 63.70 kWh (62.2/(1-.02353)) usable. I drove around the charger a little and got the used up to 62.4 with no change in DIC so that would be 63.90 kWh.
Torque said capacity est. 59.18 kWh.
Interesting! Do you have any logs from that?
 

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so that would be 63.90 kWh.
Torque said capacity est. 59.18 kWh.
Remember, GM does not give us the kWh number (only on the center screen, apparently not in an accessible PID). That came from Telek's best guess right now. He, and others change the calculation from time to time. But all use the GM PID derived Ah capacity as their starting point.
 

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I absolutely know that the Bolt HV pack has poor heat management. It's barely adequate.
The problem isn't just raw heat - the problem is temperature gradients. ...
The Bolt has large cells with only one thin aluminum plate between every other cell. The plate thus handles 2 cells and only runs down to a 1" wide interface with the heat exchanger which is only on one side of the pack...
I understand your point of temp gradients within these large individual cells (compared to Tesla's shotgun shell size cells).
You're saying if you could do rapid changes to the coolant plate temp (hot or cold), it would not be ideal for cell life.
The bottom of the cells would feel this change way before it got to the top of the cell, correct?

But I think you may have the Bolt TMS confused with the Volt's.
The Bolt only has thermal plates on the bottom that the cells sit on. I don't see any 'thin plates between cells'. There is a thermal substance between the coolant plate and the cells/modules.
Seems strange there is no thermal insulation between the aluminum coolant plate attach points to the steel bottom case of the battery pack. There is insulation under the main part of the plate and the battery case.
Here's a snip of the good Professor holding the coolant plate showing the bottom of it:
35193


If there was a way to get the battery warmer in the winter in anticipation of a DCFC session, the DCFC performance would be better.
This could be driver commanded, but adding to the driver's work load. And it would drain more power from the battery while driving and the GOM would/should ideally change immediately when the 'Warm Battery for DCFC at Next Stop' command is given. It's complicated...
I think I read Tesla's do this automatically when using Navigation for winter road trips.
 

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Discussion Starter · #1,286 ·
I understand your point of temp gradients within these large individual cells (compared to Tesla's shotgun shell size cells).
You're saying if you could do rapid changes to the coolant plate temp (hot or cold), it would not be ideal for cell life.
The bottom of the cells would feel this change way before it got to the top of the cell, correct?
Correct. The temperature of the main cooling plate would quickly affect the bottom of the cell, leaving the top of the cell much less impacted.

But I think you may have the Bolt TMS confused with the Volt's.
The Bolt only has thermal plates on the bottom that the cells sit on. I don't see any 'thin plates between cells'. There is a thermal substance between the coolant plate and the cells/modules.
It would save a lot of time if people just assumed that I knew what I was talking about :p :p :p

Here's a dissection of the pack that I personally did, should explain it pretty well. You can see the thin plate that runs between the top two cells (call them 1 and 2) with the foam between cells 2 and 3. Cell 3 has the plate on the bottom of it and the next cell would be under that. This plate is about 11" long, so it has about 12.4 square inches of aluminum (not fantastic for heat conduction) in contact with the main battery thermal plate for every 2 cells.

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Seems strange there is no thermal insulation between the aluminum coolant plate attach points to the steel bottom case of the battery pack. There is insulation under the main part of the plate and the battery case.
I suspect that's such a small area for conductivity that the strength of the structure was more important.
 

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Interesting! Do you have any logs from that?
Sadly, no. But I figured out how to do the logging to get the data into ABRP now. I'll probably have to make the same trip in a few weeks and will do logging.

But all use the GM PID derived Ah capacity as their starting point.
Yes, so it's actually the Ah that appears to read low compared to actual capacity. The Ah on my car has steadily dropped for the 5+ months since I got the car but I suspect that the actual capacity has not changed, so I don't know what's going on. I wonder if the Ah is actually some reference point that is tweaked a little depending on driving habits, dropping due to aggressive driving and increasing with conservative driving. So the car knows not to be overly optimistic for lead foot drivers.
 

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The Ah on my car has steadily dropped for the 5+ months since I got the car but I suspect that the actual capacity has not changed, so I don't know what's going on.
The Ah you get out of a battery depends on the battery's impedance, which is surely increasing over time, and on the C rate at which the Ah are pulled out. Unlike an ICE vehicle, which delivers the same gallon of fuel whether you drive at 20 mph, or 90 mph, a battery actually delivers less energy at higher discharge rates.

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This partly explains why we see bigger improvements in range when slowing down, compared to ICE vehicles.
 

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Yep, you know this stuff!
...Here's a dissection of the pack that I personally did, ... This plate is about 11" long, so it has about 12.4 square inches of aluminum (not fantastic for heat conduction) in contact with the main battery thermal plate for every 2 cells.

View attachment 35197
It's not clear.
What view of the cell pack is this. Is this View up- that's the bottom of the cells?
Or from a side?
I can see now why there is that thermal transfer sheet on the top to the coolant plate.
 

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No update on a 2020.
I went from 100% DIC (97.36% Raw) and drove it down to around 40% SoC one day and then the next day got it down to 2.353% DIC (3.445% Raw) and the display said I had used 62.2 kWh.
So I calculate 63.70 kWh (62.2/(1-.02353)) usable. I drove around the charger a little and got the used up to 62.4 with no change in DIC so that would be 63.90 kWh.
Torque said capacity est. 59.18 kWh.
Almost identical to the results for my 2020. I've done 3 run down tests this year, all very close to 63kWh. Ah pid is nearly always 185 and pid estimated capacity is 59.xx
 

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i have changed formula for this PID and i will try to do 3 consistent 100 to 2% battery drain to see if new formula is worth to be changed.
 

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But you have to know that I have put my Bolt through a lot of extreme cold weather in US and visiting my family in Canada last winter
 

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Remember, GM does not give us the kWh number (only on the center screen, apparently not in an accessible PID). That came from Telek's best guess right now. He, and others change the calculation from time to time. But all use the GM PID derived Ah capacity as their starting point.
But that is not very accurate.....any time regen is active it will lower KWH used.
That is just making more complicated to make accurate measure....but i guess it is within 1-5% depending on internal resistance....temperature and etc.
 
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